Battery & electrical questions

[coolmom42]

I have a 2014 Coachmen 21QB on a Chevy 4500 chassis, with an Onan 4KW generator.

*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

*Does the generator charge the chassis battery?

*Does the chassis alternator charge the house battery? If so, how well?

*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

*Does the converter charge the chassis battery when the RV is plugged into shore power?

*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

[Dutch_12078]

Our previous 1995 Coachmen Catalina Class A had a 200 amp fuse in the line from the house battery to the Onan generator. I didn't know it existed until the starter failed with a shorted winding and popped it. Tracing back to find out why no 12 volts from the battery finally found it tucked away in the battery compartment.

[enblethen]

The Cole Hersee style 200 amp is normally stocked at NAPA.

[pnichols]

Here's the continuous duty solenoid with silver contact surfaces that I installed in our Itasca to replace the stock solenoid ... as I was not happy about arriving at campgrounds with coach batteries that hadn't been charged by the alternator because the stock solenoid had failed. 😉 : https://www.amazon.com/Trombetta-114-1211-020-Volt-Bear-Contactor/dp/B007W2NBAU

This is the product line for the solenoid above: https://www.trombetta.com/wp-content/uploads/2019/07/bear-family.pdf

[CharlesinGA]

pnichols wrote:
Now ... what has happened twice in 15 years regarding our current motorhome's batteries getting charged by the Ford alternator ... is this: The 12V solenoid that connects the engine alternator to the coach batteries whenever the ignition key is turned on has failed, such that we arrived at our destination with coach batteries that did not get charged by the alternator.

This above situation was probably due to corroded contacts of the solenoid - because I could still hear the failed solenoid engaging when I would turn on the ignition key. I now have an after-market heavy duty 12V solenoid with silver plated contacts inter-connecting the engine alternator and coach battery bank.

What you are describing is an extremely common problem on the Winnebago manufactured motor homes. WBO used a charge/boost relay (round silver case, two large terminals and one small one, two mounting ears) that is way under capacity for what it is doing. It is 80 amp rated with plain copper contacts. The very best thing you can do is replace it with a Cole Hersee 24213 which is an identical looking relay, except it has two small terminals. You have to fabricate a short jumper from one of the small terminals to ground, usually a mounting bolt. The old relay was internally grounded to the case.

The Cole Hersee 24213 is 200 amp continuous duty rated with silver tungsten plated contacts that will probably last longer than the motorhome. It is about $50.

Amazon Cole Hersee 24213 relay

The terminals are slightly shorter and you have to be careful tightening the nuts. DO NOT allow the factory installed nuts, or the studs, to turn during tightening, use thin lockwashers and you will have just enough stud to work. I have recommended this numerous times on the major RV boards and just recently went thru a series of PM's with a gentleman who found that the relay was not functioning on his Itasca. He replaced it. This is the "standard" recommendation on the View/Navion forum, to simply replace it before it fails. The one on my '07 View was failed at 18K miles and I didn't know it because I was always using shore power to keep the battery charged via the converter. After testing and discovering the relay bad (no voltage rise across it after starting the engine) I replaced it.

Charles

[pianotuna]

bobndot wrote:
Phil, good tip on cleaning the solenoid contacts, i'll put that on my list. Tnx !

The solenoid's I've seen are sealed in and can not be serviced.

[bobndot]

time2roll wrote:
^^^^ perfect example on how all can be updated to suit your needs ^^^^^

x2, for sure , that's incredible !



Phil, good tip on cleaning the solenoid contacts, i'll put that on my list. Tnx !

[time2roll]

^^^^ perfect example on how all can be updated to suit your needs ^^^^^

[pianotuna]

Before I moved to AGM I did get 70 amps of charging. Now that doesn't happen at all which is why I've invested in a dc to DC charger. My bank is fairly large and I use it LOTS.

My OEM wire for charging is a #8 and would blow the OEM 60 amp fuse. These are hard to find. I doubled up on the #8 with a second charging path fed by the chassis battery and used twin automatic reset breakers rated at 50 amps.

I used twin solenoids rated at 200 amps contacting and have manual control of their charging.

When the battery bank was full, I'd use the excess energy to run the electric water heater. I would monitor the chassis battery voltage and shut down water heating when it displayed 12.3 volts.

I'm hoping to have 7.2 kwh of usable storage after the summer.

[time2roll]

See how fast I was corrected 😉

[bobndot]

time2roll wrote:

bobndot wrote:

Dealer is not always correct

Same applies here. :B

Yes and will usually soon get corrected.
Dealer's word just stands in the darkness.

Answers here also have no profit motive.

I think u may have taken my comment the wrong way .
I meant here like in 'me', I was goofing on myself 😉

[Newbiecampers]

2018 Coachmen 21QB on Chevy 4500 owner here. This is what applies to my unit:

coolmom42 wrote:
I have a 2014 Coachmen 21QB on a Chevy 4500 chassis, with an Onan 4KW generator.

*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

No the gen. does not have it's own battery. It uses the house battery(s)to start. If you see a battery under the chassis most likely mounted on the left-side frame rail somewhat near the generator, that is a GM option called "isolated 2nd battery." I've posted on it before in this forum.

*Does the generator charge the chassis battery?

No.

*Does the chassis alternator charge the house battery? If so, how well?

Yes. It does it so well that if the house batteries are already or mostly fully charged, on long drives (I drive 10-12+hours some days) I will disconnect the charge function (solenoid) from the chassis alternator as to not over-charge the batts. My alternator puts out 14+ volts much of the time. The GM chassis with the rv package (which coachmen usually seems to have) have a higher amperage alternator as well.

*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

I don't have a battery isolator switch between house and chassis batteries. If by chance you meant the house battery disconnect (off) rotary switch, the alternator will still charge the house batteries with that switch off.

*Does the converter charge the chassis battery when the RV is plugged into shore power?

No.

*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

Do not know. I do not recall seeing a 200amp fuse, not sure if I have one. That's a pretty hefty fuse.

[pnichols]

SJ-Chris wrote:

coolmom42 wrote:

*Does the chassis alternator charge the house battery? If so, how well?

Almost every RV is set up to allow the chassis alternator to charge the house battery. (it's a beautiful thing that comes almost for free).

I have a 2015 Thor Majestic 28a...In my experience, the chassis alternator does a great job charging the house batteries. I have a battery monitor on my house battery bank. When the house batteries are at ~50%, I have seen my chassis alternator pumping 50+ amps into my house batteries when the engine is running (even just idling).

-Chris

Chris ... the same here.

Our Class C's Ford alternator boost charges our coach batteries very well. I often just idle the V10 engine for awhile at a campsite to partially charge the house batteries. It idles very quietly and with no vibration felt inside the coach - unlike V8 powered trucks I've owned in the past. Other nearby campers should not be able to hear it running when I top up the batteries this way because we can hardly hear the engine idling when we're in camp right beside it.

I have a digital ammeter mounted on the dash that shows current flow into and out of the coach batteries, and I've seen up to 70-75 amps from the alternator going into the large AGM coach batteries with the engine idling. A complete charge of the coach battery bank by the alternator takes about three hours when driving. When the ammeter on the dash shows the coach batteries accepting only around 1 or 2 amps with the engine running, I know that the coach batteries are fully charged.

Our first motorhome (a 1969 model built on a GMC chassis) was bought from my father-in-law and for years that was his only way of charging it's coach batteries when drycamping. He thought nothing of just idling it's gas V8 engine for awhile each morning.

Now ... what has happened twice in 15 years regarding our current motorhome's batteries getting charged by the Ford alternator ... is this: The 12V solenoid that connects the engine alternator to the coach batteries whenever the ignition key is turned on has failed, such that we arrived at our destination with coach batteries that did not get charged by the alternator.

This above situation was probably due to corroded contacts of the solenoid - because I could still hear the failed solenoid engaging when I would turn on the ignition key. I now have an after-market heavy duty 12V solenoid with silver plated contacts inter-connecting the engine alternator and coach battery bank.

I also have digital voltmeters on the dash for showing both the terminal voltage of the coach battery bank and the voltage on the chassis 12V system. If these meters ever DO NOT show nearly the same voltage on both systems (i.e. 12.XX volts on the coach batteries, but 13-14.XX volts on the chassis system) with the engine running ... then I know that either the inter-connect solenoid has failed to engage, or has highly corroded contacts -> and that I'm going to arrive at my destination with coach batteries that haven't been charged while traveling.

[time2roll]

bobndot wrote:

Dealer is not always correct

Same applies here. :B

Yes and will usually soon get corrected.
Dealer's word just stands in the darkness.

Answers here also have no profit motive.

[bobndot]

Dealer is not always correct

Same applies here. :B

[klutchdust]

When my coach was on ground power the chassis battery would be dead in 2 weeks from all the parasitic drains. I plugged a battery monitor into the 120 wall outlet that were hot from the ground power and plugged the other end into the accessory port on the dashboard. Problem solved.
I like Charles recommendation when using your slides. Mine required that .